Distribution and subcellular localization of acylpeptide hydrolase and acylase I along the hog gastro-intestinal tract

The distribution of acylase I and acylpeptide hydrolase along the hog small intestine was investigated. No significant changes in their respective spe cific activity was found when the intestine was cut off and divided into ei ght segments (taken every 200 cm) so as to specifically study the duodenum, jejunum and ileum. Upon performing subcellular fractionation of hog entero cytes, it was observed that acylpeptide hydrolase is a soluble enzyme, whil e acylase I is essentially a soluble protein accounting for only 5% of the activity associated with the whole membrane fraction. The membrane-bound ac ylase I was neither solubilized by phosphatidylinositol-specific phospholip ase C from Bacillus cereus nor by detergents which are commonly used to sol ubilize alkaline phosphatase, a glycosylphosphatidylinositol-anchored prote in. When a phase separation was carried out in Triton X-114, all the anchor ed-membrane proteins of the intestinal membranes were located in the deterg ent-rich phase, while acylase I was present in the detergent-poor phase. Fi nally, the immunolabeling of intestinal cells with specific antibodies defi nitively established the cytoplasmic localization of acylase I. Acylpeptide hydrolase and acylase I therefore both are located in the enterocyte cytop lasm. (C) Societe francaise de biochimie et biologie moleculaire/Editions s cientifiques et medicales Elsevier SAS.